Human has overcome a number of diseases by chemotherapy. However, chemotherapy using conventional small molecule drugs has been afflicted with the side effects caused by the drug acting on cells other than the target cell of the therapy. In recent years, in order to overcome this adverse effect, techniques for delivering a drug to a desired cell have been developed.
One method of delivering a drug to a desired cell is the utilization of a targeting molecule specific to the cell. For instance, retinoid and its derivative are known to function as targeting molecules specific to stellate cells, extracellular matrix-producing cells in lung, bone marrow, kidney and intestinal tracts, cancer-associated fibroblasts, and cancer cells (Patent Literatures 1-9, Non-Patent Literature 1). However, there still is a need for further targeting molecules.